a. Field of the Invention
The present invention relates to slitting thermoplastic films.
More specifically, it relates to slitting a moving, stretchable, thermoplastic film prior to stretching.
B. Description of the Prior Art
Prior art includes many expedients for slitting stationary or moving materials in sheet, web or film form. Such expedients include die presses, rotary slitters, slitter discs, score slitters, slitter knives or blades, and involve such actions as cutting, shearing, perforating, and scoring. The score-cut principle makes use of back-up rolls. Practically all these actions, however, are carried out at ambient temperatures and with moving films the slit is a continuous one in the machine direction.